Process for the preparation of polymers having a polyester structure



United States Patent 3,308,097 PROCESS FOR THE PREPARATION OF POLYMERS HAVING A POLYESTER STRUCTURE Gianfranco Pregaglia and Giancarlo Pozzi, Milan, Italy, assignors to Montecatini Edison S.p.A., Milan, Italy No Drawing. Filed July 22, 1963, Ser. No. 296,470 Claims priority, application Italy, July 23, 1962, 14,721/ 62 19 Claims. (Cl. 260-63) This invention relates to a process for the preparation of polymers having a polyester structure by the polymerization of ketene CHFCO. The macromolecular compounds obtained by the process of this invention have the following regular structure:

It is known that polyesters having the structure of Formula I may be obtained by polymerizing diketene. The formation of this polyester structure may be explained when the diketene is considered to be a methylenepropiolactone OH2=CCH2 I o o0 so that the breaking of the lactone ring results in the repeating unit of the above mentioned polymer I.

It is also known that the direct utilization of ketene for preparing regular, high molecular weight polymers has not hitherto been possible, due to the high reactivity of the ketene, which causes the formation of pitchy products that cannot be easily identified.

It has been now discovered, quite surprisingly, that it is possible to polymerize ketene, under controlled reaction conditions, to obtain a linear polymer having the polyester structure of I. The formation of a polymer having the above-mentioned structure could not be foreseen because it is derived from the enchainment of monomeric units alternatively formed through the opening of the C C and C=O bonds. The possibility that diketene of II may be a stable intermediate during the polymerization of the ketene has been rejected because of the fact that the diketene does not have a tendency to polymerize according to the process described herein.

The process of this invention is characterized by the use of a particular class of catalysts and by the nature of the reaction medium. The catalysts capable of polymerizing the ketene according to the above-mentioned process are compounds which act as anionic components under the reaction conditions. Particularly suitable are the basic compounds such as the hydroxides of the metals of Groups I and II of the Mendeleefi Periodic Table. These compounds include LiOH, NaOH, KOH, Ca(OH) and Ba(OH) In adidtion, some of the organic bases can also act as a catalyst provided that their basic constant is low enough. Thus, for example, one possible compound, in particular, is triphenylamine. Other compounds which act as anionic catalysts in the process of this invention, include the alkali metals and the alkaline earth metals, their oxides and hydrides. Still other substances include the organometallic compounds characterized by the formula R Me, where Me is a metal of the Groups I and II of the Mendeleetf Periodic Table, n is the valence of the metal and R is an alkyl, aryl, alkoxy or an alkylcarboxylic group containing from 1 to 8 carbon atoms. In adidtion to these, basic aluminum oxide was found to be an active catalyst.

In regard to the reaction medium to be used with the catalyst in the process of this invention, it was found that its action is essential and the medium must contain a polar solvent having a dielectric constant of at least 8 or 3,308,097 Patented Mar. 7, 1967 ICC higher in order to obtain a high-rate of polymerization and a minimum of side reactions.

In fact, it was discovered that in the absence of any solvent the polymerization did not occur. Moreover, in the presence of a nonpolar solvent, when a heterogeneous catalyst was used, the ketene did not polymerize in any remarkable amounts. Still further, when a homogeneous catalyst was used the polymerization started but stopped quickly and a polymer was obtained which had a high ash content, an irregular structure and was soluble in methanol.

In comparison, by operating in accordance with the process of this invention i.e., in the presence of a polar solvent having a high dielectric constant only small amounts of the catalyst were needed to promote polymerization of the ketene at a high rate and with almost complete conversion. In fact, at times the alkalinity of the glass walls of the reactor was sufiicient to start a partial polymerization.

However, the best reaction conditions were obtained when an insoluble catalyst selected from the above-identitied anionic catalyst was used. In some instances, a catalyst may be used which becomes insoluble during the polymerization. This may be due to the catalyst reacting with the solvent. The amount of catalyst ranges from about 0.1 to 0.00001 gram of catalyst per gram of monomer.

It is preferred to use polar solvents which do not contain functional groups capable of reacting with the ketene under normal polymerization conditions. The preferred polar solvent for purposes of this invention include for example the ketones such .as acetone, methylethylketone, cyclohexanone, and cyclopentanone. Other solvents include the anhydrides of acids such as, for instance, acetic anhydride and isobutiric anhydride. In addition, the nitriles such as acetonitrile and acrylonitrile have proved particularly suitable. It has been found that it is possible to work below the crystallization temperature of' these solvents by using a mixture of compounds so that the dielectric constant of the solution is sufficiently high. For

example, ketene can be added to a solution of ethyl ether and acetonitrile, which does not crystallize at temperatures at 50 C., and thus it is possible to polymerize the monomer.

The temperature within which the polymerization of the ketene takes place ranges from about to +20 C. but more preferably between 100 and 45 C. It is also important to note that the ketene used in the polymerization reaction, may be obtained directly from the pyrolysis of acetone or acetic acid, without the necessity of going through a particular purification process which is a costly intermediate operation.

The polyketenes obtained by the process of this invention have a crystallinity in excess of 40% and are soluble in warm chloroform, benzene and dioxane at temperatures of at least 40 C. These polyketenes have molecular weights ranging from about 500 to 5000 and melting points lower than 100 C.

It has been found that it is possible to mix the polyketenes of this invention with other polymers not easily dyed so that the reactivity of the methylene groups along the main chain of the polyketene impart the necessary aflinity for the dyes.

The following examples are for purposes of illustrating the invention.

Example 1 Approximately 35 cc. of anhydrous acetone and 2 grams of KOH pellets were introduced into a 250 cc. three-necked flask provided with a mechanical stirrer and cooled to a 70 C. A gas stream coming from an apparatus for acetone pyrolysis was bubbled into the flask. A white precipitate was formed which quickly increased to the extent that the reaction mixture became a pasty 4 the Mendeleeff Periodic Table, 11 is the valence of the metal, and R is selected from the group consisting of alkyl and alkoxy groups containing 1 to 8 mass. After about 1 /2 hours the gas stream was intercarbon atoms; rupted and the mass was treated with acetone which had (c) alkali metals, oxides, and hydrides; been previously cooled. The KOH pellets were mechani- (d) alkaline earth metals, oxides, and hydrides; cally separated, and the polymerization mass was poured (e) triphenylamine and into methanol. After a quick filtration, the mass was (f) basic aluminum oxide thoroughly washed with methanol and dried. Approxiat a temperature ranging from about 100 to +20 C. mately 14.4 grams of the polymer were obtained which 10 2. The process of claim 1 further characterized in that indicates that approximately 75% of the monomer was h polar solvent is a k tone. converted. The crude polymer was found to be soluble 3. The process of claim 2 further characterized in that in chloroform, dioxane, tetrahydrofurane, but insoluth polar v nt is acetone. ble in ether, heptane and cyclohex'ane. 4. The process of claim 2 further characterized in that The melting point of the product as determined on a the Polar Solvent is cycloheXanone- C pp r block Was about 60 C. The polymer was noti ed 5. The process of claim 2 further characterized in that to release gaseous products at temperatures only in exthe polar solvent is methylethylketone. Cess of 100 C. This particular polymer had a, molecular 6. The pIOCESS of claim 1 further characterized in that weight of about 1,000, as determined by the cryoscopic the anionic catalyst is a hydroXide Of a metal of Groups method in dioxane, 'and under an X-ray examination I and II Of the Mendelceff Periodic Table. clearly exhibited crystallinity. The IR. spectrum showed 7. The process of claim 6 further characterized in tha absorption bands at 5.65 microns which may be attributed the anionic ly i lithium hy r xi to h 3:0 bonds and at 3 555 microns hi h may b 8. The process of claim 6 further characterized in that attributed to the c o c group. The band at 5.99 t anionic catalyst ispofassium hydroxidemiCr nS may be attributed to the CH =C bond. 9. The process of claim 1 further characterized in that Examples 241 the anionic catalyst is an organometallic compound having the formula R Me wherein Me is a metal of Groups Into a 100 cc. glass tube provided with a side cock for I and II of the Mendeleeff Periodic Table n is the the introduction of nitrogen, the catalyst and a solvent valence of the metal and R is selected from the group conin an amount, by volume, twice the amount of ketene sisting of alkyl, and alkoxy containing from 1 to 8 carbon were introduced under an inert atmosphere. The ketene atoms. was distilled while keeping the reaction mass at a tem- 10. The process of claim 9 further characterized in that perature of a 78 C. The polymer obtained was R is an alkyl group. washed with methanol and dried. The following table 11. The process of claim 9 further charatcerized in that lists the data of the various tests. the. R is an alkoxy group.

TABLE 1 Example Conversion of Reaction No. Monomer, cc. Catalyst Solvent monomer, time, hrs.

percent 12 LiC-iH9,6.10- mols Acetone 8.8 0.5 14 LiC4H9,fi.1O mols. Cyelohexanone 7.8 1.5 14 LiCqHQ, 6.10 mols Methylethylketone 12 1 9 CiH oLi, 5.10- mols l. 2 1 s CHsONa, 10.1(Hmo1s..- 8.7 3 s LiOH,8.10- mols 2e 48 10 A1203 (basic),810- 111ols 20 1 8 Li, 2.1M 1nols 21.5 16 8 K, 4.10' 1nols 21.5 24 10 Na-isoamyl, 5.10- mols 8.5 6

While this invention has been described with respect to a number of specific examples, it is understood that other variations and modifications may be used without deparing from the spirit and scope of the invention, except as recited in the appended claims.

What is claimed is:

1. A process of preparing ketene polymers having essentially a polyester structure having the formula:

12. The process of claim 10 further characterized that the catalyst is butyl-lithium.

13. The process of claim 10 further characterized that the catalyst is amyl sodium.

14. The process of claim 11 further characterized that the catalyst is lithium butylate.

15. The process of claim 11 further characterized that the catalyst is sodium methylate.

16. The process of claim 1, further characterized that the anionic catalyst is an alkali metal.

17. The process of claim 16 further characterized that the alkali metal compound is lithium.

18. The process of claim 16 further characterized that the alkali metal compound is potassium.

19. The process of claim 1 further characaterized that the anionic catalyst is basic alumina.

References Cited by the Examiner FOREIGN PATENTS 893,308 4/1962 Great Britain.

WILLIAM H. SHORT, Primary Examiner.

C. A. WENDEL, Assistant Examiner. 

1. A PROCESS OF PREPARING KETENE POLYMERS HAVING ESSENTIALLY A POLYESTER STRUCTURE HAVING THE FORMULA: 